A little of both? The flying off the bikes is minimal. There is a scene or two with the bad guy beating people up/getting beat upon, for very nefarious purposes.

They made a big deal out of "Wylie has a death wish! He rides a fixed gear bike with no brakes!" It was cool. Also they showed a brief outtake at the end where he clearly did his own stunt and broke the windshield of a taxi.